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# Object is placed on the principal axis of a concave mirror. Its real image is formed at a point which is 10 cm more distant from the mirror than the object. If focal length of mirror 12 cm. The magnification of the image is:

A
2
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B
1.5
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C
1
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D
2.5
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Solution

## The correct option is B 1.5Given: Focal length, f=−12 cm Object distance =−u Image distance (v) is 10 cm more than the object distance ⇒v=(u+10). Real images for concave mirrors are formed on the same side as the object for concave mirrors. Using mirror formula, 1u+1v=1f 1−u+1−(u+10)=1−12 Simplifying, u2−14u−120=0 u2−20u+6u−120=0 (u−20)(u+6)=0 Object distance is taken as −u. Hence, u is positive. ⟹u=20 cm Hence, image distance is: v=−30 cm Magnification is given by: m=−Image DistanceObject Distance m=−−30−20=−1.5 Magnitude of magnification is: |m|=1.5  Suggest Corrections  0      Similar questions  Related Videos   Lens Formula, Magnification and Power of Lens
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